It may be responsible for the synthesis of the sequence NeuAc-alpha-2,3-Gal-beta-1,3-GalNAc- found in terminal carbohydrate groups of certain glycoproteins, oligosaccharides and glycolipids. SIAT4A and SIAT4B sialylate the same acceptor substrates but exhibit different Km values.

Tissue specificity

Highly expressed in skeletal muscle and heart and to a much lesser extent in brain, placenta, liver and pancreas. Scarcely detectable in lung and kidney.

Pathway

Protein modification; protein glycosylation.

Sequence similarities

Belongs to the glycosyltransferase 29 family.

Post-translationalmodifications

The soluble form derives from the membrane form by proteolytic processing.